how to lose double chin while getting bigger

Can anyone help me with this problem? Im a skinny guy trying to put on muscle but I have a double chin that really bothers me and only a small amount of abdominal fat. Been primal for nearly 2 months now, doing the exercises in the PB fitness ebook. Had been doing other gym programs for 10 years prior with the normal grains, veg, fruit, meat, low fat diet with no real muscle gains. The PB fitness I think has made my biceps bigger than usual slightly and is improving my stamina.

Whatever you do, keep up the resistance training. Building or at least maintaining muscle mass is key whatever your goal is, and you can't do that without resistance training.

If you are new to strength training and/or have a good bit of excess bodyfat, you can build muscle and lose fat "simultaneously". I use quotes because these two processes do not occur at the same instant, but both can happen over the course of a day and the cumulative effect of each process is a net gain in muscle and loss of adipose tissue. I am personally a fan of the Leangains method, but it is certainly not the only way.

If you have been seriously strength training for some time and/or you are already quite lean, you will do better to focus on either building muscle or losing fat instead of trying to do both. You can lose fat for a few months (while maintinaing your muscle mass), then switch to building muscle. The key to either one is "slow and steady wins the race". If you create a huge caloric defecit, you WILL lose some muscle mass. Flipside: if you create a huge surplus, you will gain fat. If you have just a slight defecit/surplus, your results will be much better in either case.

From the limited information provided, my recommendation would be to start a serious barbell strength training program, focusing on squats, deadlifts, overhead presses, chinups, etc (Google Mark Rippetoe Starting Strength...or just buy the book). And to create a slight caloric defecit so that you lose body fat slowly. Good luck and keep us appraised of your progress!